A USB drive -- also known as a flash drive or keychain drive is a plug and play portable storage device that uses flash memory and is lightweight enough to attach to a key chain.

When the user plugs the device into the USB port, the computer's operating system recognizes the device as a removable drive and assigns it a drive letter.

Unlike most removable drives, a USB drive does not require rebooting after it's attached, does not require batteries or an external power supply, and is not platform dependent.

Several manufacturers offer additional features such as password protection, and downloadable drivers that allow the device to be compatible with older systems that do not have USB ports.

USB drives are available in capacities ranging up to about 65 gigabytes (GB), depending on manufacturer, in a corresponding range of prices.